# When photons enter a non-vacuum medium, can they be said to have mass?

Photons travel at less than the speed of light (in a vacuum), so anything travelling at less than SOL is supposed to have mass. Could it be said that the electromagnetic permittivity and permeability of a medium acts sort of like a Higgs field for photons, and gives it a type of mass?

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• Light particles are the most dense particle structure in the Universe.Their volume is approx 1 x 10^- 105 cubic meters.

In reality a pure vacuum does not exist in the physical Universe.

What space is made of is another type of mass having a much more smaller volume.

Mass according to Maxwell is defined as volume divided by the square of time.

In relativistic terms mass is not exactly mechanically defined .Hence few are deemed to understand what relativistic mass means. Something which has no mass cannot be explained mechanically as existing .

If photons had no mass they could not bounce off the wall.

Higgs particles have not been exactly proved that they exist as Bosons.

The speed of light is variable depending on the strength of the gravity field of the medium and magnetic field its traversing. Einstein equation for the speed of light in a gravity field is as follows; C' = C + square root of Phi.

where phi is the gravity field energy potential

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• photons DO HAVE MASS IN VACCUUM they do NOT HAVE REST MASS.. they are always moving... so they always hve relitavistic mass

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• No, but that photons supposedly have no rest mass is an ASSUMPTION made to make the math a little less complicated. The problem with photons is you cannot pin them down long enough to measure their rest masses without destroying them or running into the Heisenberg uncertainty principle. The speed of photons slows down because of quantum interference with the weak and strong forces of the atoms of the medium. Some minerals have three speeds of light.

• Quit trying to provoke
These are confirmed scientific facts. I dare you to take a mineralogy course and get an A- in it like I did in fall 1977. Your comment proves you know I am correct.

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• No. In a material, photons travel at the usual speed of light between atoms but sometimes an atom absorbs the photon. It then re emits it. But this takes some time. So it just seems like light is slowed down.

• Nope, that's a high-school oversimplification.

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• It is much more helpful to think of refraction as a wave phenomenon, where the group velocity is less than c. The problem with the photon picture and slowing down in a material is: how does it accelerate again to c after leaving the medium....

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